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MG MGF Technical - Battery drain

I know this has been covered many times, but having tried all the suggestions listed in previous threads, my problem remains.

My 2001 ‘F was off the road for the 6 months to May. During this time I had it running for a few minutes most weeks and it always started without too much trouble. Since it’s been back on the road however, it will not hold its charge. The battery will completely drain overnight.

I have replaced the battery twice. The battery earth lead appears to be in good condition. I have checked all obvious things like lights (boot, interior, bonnet etc), checked the MEMS relay pack (no obvious sign of any problems & nice clean contacts), checked wiring (some of the wires running into the boot had broken but have been fixed), there is no problem once started suggesting the alternator is fine (I measure a 13.5 approx charge at idle, 12V approx when not running). Locking the car by key (ie. without the alarm) helps but only gives an extra few hours. Removing the 2nd fuse from the left makes no difference.

The ammeter measures a 0.29A or so current drain - (though I haven’t managed to measure the expected drop after 15 minutes as suggested in some threads).

Last week Mike Satur had the car and ran tests without finding anything.

Not sure if this is relevant, but the radio has also developed an annoying buzz on most FM stations.

As Im left with jump-starting it every day, I would be grateful for any ideas.

Nick
N Parr

>> The ammeter measures a 0.29A or so current drain - (though I haven’t managed to measure the expected drop after 15 minutes as suggested in some threads). <<

This is worth checking - if the current drain remains high after 15min, it either suggests that there is a short circuit somewhere (most likely in the boot wiring loom adjacent to the hing), or that MEMS is not switching off as it should (this has been known).

Everything else, as you say, sounds normal...
Rob Bell

With the ammeter connected, pull fuses out one at a time to try and identify the circuit that's pulling the current.
Or did mike try that?

If it's the MEMS not shutting down - could be a sticky relay that just need a good clout :-)

jt
John Thomas

Is that <point>29 Amps ?
or about 3.5Watts. Even if that is slightly above normal, then the battery should be able to maintain that drain for several days and then start the car on a normal summer's morning.
What state is the battery in the next day ?

Try measuring its voltage 1 hour after you switch off, and then again next morning. Battery should read about 12.6V (2.1V per cell) within the first hour or so after charge. The battery should then maintain at least 12.0V during the major part of its discharge cycle. At around 10.8V, the battery may be regarded as fully discharged - it should not be taken beyond this point. It will drop from 12.0 towards 11 fairly quickly.

The charging voltage needs to be about 14.4V (about 2.4V per cell) to fully charge - may need higher revs to check this.

You might try disconnecting the battery and checking that it maintains about 12.6V.

There's lots of stuff in the archive about checking the MEMS current drain - I would guess that you still need to check that out.
Steve

Thanks for the ideas.

I finally traced the problem to the (factory fitted) radio, and a dodgy live wire. Even though the radio was switched off it was still drawing power - once disconnected the drain dropped from 0.29A to a more reasonable 0.01A.

Oddly, its still not sorted the 'buzzing' that I get on all FM stations. However, if the car starts then I can live with the buzzing.



N Parr

Time to change the head unit? I am sure that original standard units are available very cheaply if you want to keep the original looks - or you can simply upgrade to a more modern unit (the connectors are all industry standard ISO)
Rob Bell

Check the chassis of the radio is earthed directly and not just through the aerial at the rear of the car. If the current for the radio has to run along the braided outer screen of the aerial then it can cause the symptoms you describe. Unplug the aerial at the back of the radio and make sure your tape/cd whatever still works. If it doesn't then that's the problem.

HTH

Bruce
Bruce Caldwell

If you are leaving your car standing for this amount of time, you are going to get a breakdown in battery condition. The best idea is to install a trickle feed system to keep the battery up to scratch. I have the same problem. During the winter I rarely drive the F - if it gets wet it might shrink. A trickle feed keeps my battery in excellent condition and no problems. The system I use has a 12 volt step down type charger similar to a cell phone charger with charge point installed near the battery- Must however remember to disconnect before driving off

Hope this helps

David
David Richards

That's a great solution David :o) But what about those of us without a garage for their precious MG?
Rob Bell

Remove house front door, remove door frame, remove sufficient bricks to allow access for F, send wife shopping .....
Get your priorities right
K Waring

ROFL
Rob Bell

Ok you win Do like the idea of getting priorities right

How about trickle feed solar panel- available here for about $100 - attach to your hood protector

What I hear you say - we have no sun.

The come over here or even better come to Aussie

No more good ideas - sorry guys

David
David Richards

David,

$100!!!!!! I'dont think so :-)

Here check this out. A bit better priced.
Post to NZ would not be that much on top of the price
I actually bought one some time ago Goes well.

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=4566481221

Cheers
Branko.
Branko

Hi Branko

Actual price direct from Dick Smith $50.82 + 12.5% These are 2 watt.

Main thing is to get those poms educated into alternative technology (TIC)


David
David

This thread was discussed between 29/07/2005 and 07/08/2005

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